Flooding Time Research Articles

Hydroperiod modulates early growth and biomass partitioning in Rhizophora mangle L.

In mangrove forests, the hydroperiod is strongly related to tidal dynamics, where the periodic oceanic water movement regulates the level, duration, and frequency of the flooding events. In fringe mangrove forests, Rhizophora mangle propagules deal with variable hydroperiod conditions that sometimes compromise their survival. To disentangle the combined effects of duration and intensity of flooding on physiological and growth variables, we imposed a continuous experiment with three levels of flooding and four flooding durations on seedlings of R. mangle. We collected data at 3 and 6.5 months after exposure to the treatments. Propagule reserves allowed plants to evade the effects of the flood level after a 3-month treatment period. After a 6.5-month exposure, physiology and growth were modulated by the flooding time. Individual plants had higher stem length and lower root and total biomass at prolonged and high flooding levels compared to any other flooding combinations. In both ages, the highest total plant biomass was exhibited in the medium flooding levels and 6 h flooding duration. The plasticity index was higher for morphological and biomass variables than for physiological variables. The high morphological plasticity of R. mangle plants constitutes a competitive advantage to colonize flooded sites in fringed mangrove areas. Our results identify schemes to improve the success of mangrove restoration plans, a critical tool for carbon sequestration and ecosystem service provision.

Understanding the density patterns of the polychaete Diopatra neapolitana and its relationship with environmental factors in the NW Spain

To understand the density patterns of the tube-forming polychaete Diopatra neapolitana and their relationship with environmental factors, an extensive sampling was conducted in an intertidal, commercially exploited population in the Ría de Vigo (NW Spain). Interpolation of the sampled densities was carried out by Inverse Distance Weighting (IDW). The results showed a heterogeneous, patchy distribution: the average density was 2.56 tubes/0.25 m2, although some areas exhibited a density with more than 30 tubes/0.25 m2 while in others the species was completely absent. Our data also showed that the presence of vegetation (either algae or Zostera) increased the densities of D. neapolitana. To better understand this finding, a second sampling was conducted targeting the three main permanent habitats identified in the study area. This revealed that the spatial location within the intertidal was the most important factor affecting densities. The higher densities observed with increasing latitude and longitude are a consequence of the higher flooding time, that means less water stress and longer submergence time, and involves a reduced likelihood of being caught by shellfish harvesters. The second most important factor explaining D. neapolitana densities was the sediment organic matter content, which is consistent with the observation that the presence of vegetation increases the density of tubes. This work is the first comprehensive approach to understand the spatial structure of densities of D. neapolitana.

Quantitative understanding of the impact of flooding durations on Cd variations in an acidic paddy soil during the flooding and drainage processes

The solubility and transformation of cadmium (Cd) are controlled by paddy soil pH, whereas paddy soil pH varies during flooding and drainage and is significantly controlled by flooding durations. However, there is still a lack of modeling approaches for simulating the impact of flooding durations on pH fluctuation and concomitant Cd effectiveness in Cd-polluted acidic paddy soils. Herein, laboratory findings combined with a process-based numerical modeling method were used to quantify the observed key geochemical processes of Fe/C/N/S and the accompanying Cd partitioning dynamics during flooding and drainage. During flooding stage, the number of protons consumed by Fe(III), NO3−, and SO42− reduction increased with flooding durations, resulting in an increase of pH, which enhanced Cd immobilization and reduced Cd potential risk. After entering drainage stage, the number of protons released from Fe(II), NH4+, and S2− oxidation increased with flooding time, leading to pH decrease, which increased Cd release. A process-based kinetic model fitting results showed that Fe(III) reduction and Fe(II) oxidation were key processes that increased and decreased pH, respectively, and that increasing flooding durations were not beneficial to Cd immobilization during flooding and drainage processes. The results of this study shed light on the impact of redox state of paddy soil on Cd dynamics under different flooding durations and provide a theoretical approach to quantify the contribution of key processes controlling changes in metal species, which can be used to simulate the dynamic behavior of heavy metals in paddy soil under different natural conditions by coupling other significant processes.

Research on the Timing of WAG Intervention in Low Permeability Reservoir CO2 Flooding Process to Improve CO2 Performance and Enhance Recovery

In low permeability reservoirs, CO2 flooding usually leads to gas channeling, whereby a significant amount of CO2 bypasses the oil-bearing formation and fails to effectively displace oil. Introducing water-alternating-gas (WAG) flooding, utilizing water phase stability-driven processes, serves to suppress gas channeling and enhance oil recovery rates. Implementing WAG flooding, which utilizes water phase stability-driven processes, helps suppress gas channeling and improve oil recovery rates. The timing of implementing WAG flooding is crucial. Initiating WAG flooding prematurely can limit the efficiency of CO2 displacement, while initiating it with delays may result in severe gas channeling, resulting in decreased production and increased environmental risks. Finding the balance point is the challenge. The balance point can effectively control gas channeling without reducing the efficiency of CO2 flooding. In this paper, the timing of WAG flooding in low permeability reservoirs is studied in detail. Firstly, this study conducted experimental research to investigate the CO2 displacement process in both homogeneous and heterogeneous cores. Furthermore, it validated the correlation between the timing of WAG injection and the heterogeneity of the cores. The experimental results indicated the existence of an optimal timing for WAG injection, which is correlated with the degree of heterogeneity. Numerical simulation studies were performed to simulate the characteristics of the light oil–CO2 system using the Peng–Robinson (PR) equation. Furthermore, a history matching analysis was performed to validate the experimental results and investigate the correlation between WAG injection and the degree of heterogeneity. The study concluded that as the degree of heterogeneity increases, initiating WAG injection earlier leads to a more significant suppression of gas channeling, increased water–gas interaction, improved gas–oil contact, and enhanced the synergistic effect of increasing the resistance and pressure of WAG flooding and controlling gas channeling. This finding has significant practical implications, as the optimization of WAG injection timing can enhance oilfield production efficiency.

Nitrogen availability affects the responses of marsh grass and sedge plants (Phragmites australis and Bolboschoenus planiculmis) to flooding time

Flooding time and external nitrogen (N) input have been projected to be the main threats to marsh ecosystems in the scenario of more intense flooding events and N deposition. How flooding and N addition experienced at different growth stages interact in determining phenotypic change remains scarce. We established a controlled experiment (3 flooding time treatments x 5 N addition levels) using two herbaceous marsh species (Phragmites australis and Bolboschoenus planiculmis) to assess the responses of six key traits to environmental changes and the indication of plant performance. Early flooding reduced plant height and aboveground biomass of P. australis and below/aboveground biomass ratio of B. planiculmis and increased below/aboveground biomass ratio of P. australis and root biomass of B. planiculmis, whereas late flooding reduced root biomass of P. australis and ramet number and aboveground biomass of B. planiculmis. The combination of flooding and high N (16 and 32 g N m−2) exerted negative effects on ramet number of both plant species. The interaction of early flooding and low-medium N (8 and 16 g N m−2) inhibited clonal/belowground biomass ratio of both plant species. The combination of early flooding and low N (0, 4 and 8 g N m−2) promoted root biomass and below/aboveground biomass ratio of P. australis. Ramet number, plant height, and root biomass explained 80–90 % of aboveground biomass variation of both plant species, and the contribution of ramet number was greater than that of the other two traits. These results highlight that the influence of flooding time and external N input on the performance of marsh plants depends on species identity. Meanwhile, the ramet number-plant height-root biomass (RHR) strategy is supposed to be the adaptation strategy of wetland clonal plants to environmental changes, and clonal reproductive traits should be incorporated into vegetation dynamics models for marsh plants.

Application of Gated Recurrent Unit Neural Network for Flood Extraction from Synthetic Aperture Radar Time Series

Floods are a sudden and influential natural disaster, and synthetic aperture radar (SAR) can image the Earth’s surface almost independently of time and weather conditions, making it particularly suitable for extracting flood ranges in time. Platforms such as Google Earth Engine (GEE) can provide a large amount of SAR data and preprocess it, providing powerful assistance for real-time flood monitoring and time series analysis. However, the application of long-term series data combined with recurrent neural networks (RNNs) to monitor floods has been lacking in current research, and the accuracy of flood extraction in open water surfaces remains unsatisfactory. In this study, we proposed a new method of near real-time flood monitoring with a higher accuracy. The method utilizes SAR image time series to establish a gated recurrent unit (GRU) neural network model. This model was used to predict normal flood-free surface conditions. Flood extraction was achieved by comparing and analyzing the actual flood surface conditions with the predicted conditions, using a parameter called Scores. Our method demonstrated significant improvements in accuracy compared to existing algorithms like the OTSU algorithm, Sentinel-1 Dual Polarized Water Index (SDWI) algorithm, and Z-score algorithm. The overall accuracy of our method was 99.20%, which outperformed the Copernicus Emergency Management Service (EMS) map. Importantly, our method exhibited high stability as it allowed for fluctuation within the normal range, enabling the extraction of the complete flood range, especially in open water surfaces. The stability of our method makes it suitable for the flood monitoring of future open-access SAR data, including data from future Sentinel-1 missions.

Pemodelan Genangan Banjir Sub DAS Bengkulu Hilir Provinsi Bengkulu Menggunakan Program Hec-Ras 5.0.7 Berbasis Ras Mapper dan Arc-Gis 10.8

The Down Stream Air Bengkulu Watershed is part of the Air Bengkulu Watershed in Bengkulu Province. Flooding in this area frequently leads to major subdistrict, economy, and environmental impacts. The aim of the research is to develop a flood forecasting model that is capable of mapping potential flood areas in order to support flood control efforts. The method used is a hybrid model between a hydrological model, a hydraulics model and a Geographic Information System (GIS). The hydrological model is input to HEC-RAS software, It’s developed based on Snyder's Synthetic Unit Hydrograph (SUH). The hydraulics model was prepared using the software of HEC-RAS version 5.0.7 and the it’s output was used as material for preparing potential flood inundation maps. The potential flood inundation map was prepared by overlay method with the help of the Arc-GIS version 10.8 application. The research results show that the peak flood time is 7.43 hours with peak discharge for a 100 year return period of 1,542 m3/second. Flood inundation occurred in nine sub-Districts including Talang Empat District (552,819 ha), Karang Tinggi (391,648 ha), Selebar (24,118 ha), Singaranpati (95,806 ha), Ratu Samban (6,838 ha), Ratu Agung (212,173 ha), Sungaiserut (541,659 ha), Muara Bangkahulu (395,495 ha), and Pondok Kubang (197,167 ha). The conclusion of the research is that the model developed is able to answer peak times, area and water level of inundation as well as potential locations that will be flooded.

The Pattern of Morbidity and Access to Healthcare Service in the Riverine Flood-prone Villages of Assam, India

Background: Floods are considered one of the common phenomena causing substantial death, morbidity, and damage to infrastructure as well as economic conditions across the world. India receives 75% of its total rainfall in the monsoon season, as a result, annually on average 8 million people are affected by the floods. The Brahmaputra valley of Assam is one of the worst flood-affected regions in the country. This study focuses on understanding the pattern of morbidity, health service utilization, and challenges faced to access healthcare services in the riverine flood-prone villages of Assam. Methods: A mixed method study was followed to conduct the study. Primary data have been collected through interview schedules from 83 households. Descriptive statistics of both frequency and percentage were shown for categorical as well as continuous variables. Qualitative data were analyzed using a thematic framework. Results: The research findings indicate that in the flood-prone villages people face difficulty in accessing healthcare. However, the challenges intensify during flood times. It was identified that illnesses like fever, skin infection, diarrhea, and dysentery are linked to floods. Three themes were identified from the qualitative analysis i.e., lack of transportation facilities, non-functional sub-centres, and lack of money. The transportation facilities and the non-functional sub-centers were some of the causes along with the financial constraint to avail the health care facilities. Conclusion: It can be concluded that to improve the health service condition in the flood-prone areas, there is an urgent need to improve both the quality and quantity of the sub-centres infrastructures and the manpower. Other public health interventions such as providing food, water, and shelter, especially during floods need to be developed. Encouraging early flood preparedness and public health awareness programs through community participation would also help to reduce the damage to these people.

Sequential riparian vegetation alteration in Japanese river landscapes

Bare gravel bed channels have been a common landscape feature of the middle reaches of rivers throughout Japan. They are disappearing these days because of vegetation colonization. Vegetation coverage of the riparian zones in the midstream reaches of rivers distributed throughout Japan was investigated using aerial photo images taken in 1946, 1975, and 2010. It was then compared with hydrological and water quality records, locations of dams and weirs, residential conditions of the surrounding areas, sediment yields, and forest coverage of the upstream mountainous areas. Riparian vegetation coverage has substantially increased in the last 70 years, from nearly 0 to 30-40%. Herbaceous vegetation coverage is higher than tree coverage. The total vegetation coverage did not correlate with water quality parameters. However, vegetation coverage had a significant negative correlation with the upstream basin's sediment yield and a slight negative correlation with the maximum flood peak flow rate. It was positively correlated with the terrestrial area fraction between levees. Riparian vegetation coverage was high within the 2 km downstream of dams or weirs, intercepting sediment flows. These results indicated that the gravelly sediment supplied from the upstream and deposited in the midstream at flood time has been the major contributor to keeping the vegetation coverage low rather than flushing by flood water. Reforestation since World War II has reduced the coarse sediment supply into the midstream river channels. This reforestation, together with gravel mining and intercepting sediment flow by dams and weirs, has caused the recent increase in vegetation coverage of the riparian zones. Human intervention can affect the vegetation conditions in riparian zones by decreasing sediment supply to river channels.

Changes in Magnitude and Shifts in Timing of Australian Flood Peaks

We analysed changes in magnitude and timing of the largest annual observed daily flow (Amax), in each water year, for 596 stations in high-value water resource catchments and flood risk locations across Australia. These stations are either included in the Bureau of Meteorology’s Hydrologic Reference Stations or used in its operational flood forecasting services. Monotonic trend (which is either consistently increasing or decreasing) analyses of the magnitude and timing of flood peaks (estimated using Amax) were performed using the Theil–Sen and Mann–Kendall approaches and circular statistics to identify the strength of seasonality and timing. We analysed regional significance across different drainage divisions using the Walker test. Monotonic decreasing trends in Amax flood magnitude were found in the Murray–Darling River Basin and in other drainage divisions in Victoria, southwest and midwest of Western Australia and South Australia. No significant obvious pattern in Amax magnitude was detected in northern Queensland, coastal NSW, central Australia and Tasmania. Monotonic increasing trends were only found in the Tanami–Timor Sea Coast drainage division in northern Australia. Monotonic trends in Amax magnitude were regionally significant at the drainage division scale. We found two distinct patterns in flood seasonality and timing. In the northern and southern parts of Australia, flood peaks generally occur from February to March and August to October, respectively. The strength of this seasonality varies across the country. Weaker seasonality was detected for locations in the Murray–Darling River Basin, and stronger seasonality was evident in northern Australia, the southwest of Western Australia, South Australia, Victoria and Tasmania. The trends of seasonality and timing reveal that in general, flood peaks have occurred later in the water year in recent years. In northern Australia, flood peaks have generally occurred earlier, at a rate of 12 days/decade. In Victoria, New South Wales and Tasmania, the trends in timing are generally mixed. However, in the southwest of Western Australia, the largest change in timing was evident, with Amax peaks commencing later at a rate of 15 days/decade. Decadal variability in flood timing was found at the drainage division scale as well. Most stations show a decreasing trend in Amax magnitude, but how that trend is associated with the change in timing is not clear.

Dynamic Production of Hydroxyl Radicals during the Flooding-Drainage Process of Paddy Soil: An In Situ Column Study.

Frequent cycles of flooding and drainage in paddy soils lead to the reductive dissolution of iron (Fe) minerals and the reoxidation of Fe(II) species, all while generating a robust and consistent output of reactive oxygen species (ROS). In this study, we present a comprehensive assessment of the temporal and spatial variations in Fe species and ROS during the flooding-drainage process in a representative paddy soil. Our laboratory column experiments showed that a decrease in dissolved O2 concentration led to rapid Fe reduction below the water-soil interface, and aqueous Fe(II) was transformed into solid Fe(II) phases over an extended flooding time. As a result, the •OH production capacity of liquid phases was reduced while that of solid phases improved. The •OH production capacity of solid phases increased from 227-271 μmol kg-1 (within 1-11 cm depth) to 500-577 to 499-902 μmol kg-1 after 50 day, 3 month, and 1 year incubation, respectively. During drainage, dynamic •OH production was triggered by O2 consumption and Fe(II) oxidation. ROS-trapping film and in situ capture revealed that the soil surface was the active zone for intense H2O2 and •OH production, while limited ROS production was observed in the deeper soil layers (>5 cm) due to the limited oxygen penetration. These findings provide more insights into the complex interplay between dynamic Fe cycling and ROS production in the redox transition zones of paddy fields.

Two-parameter family of distributions: Properties, estimation, and applications

In this paper, a new flexible two-parameter family of distributions is introduced. Some mathematical properties, such as asymptotic behavior, moments, stochastic order, entropy, and quantile function, are examined. A special case of this family is introduced called Gemeay–Zeghdoudi distribution. The unknown parameters of the Gemeay–Zeghdoudi distribution are estimated via many estimators. The efficiency of the estimators is compared with a Monte Carlo simulation. The applicability of the new distribution is illustrated by the annual maximum flood and survival times of patients with breast cancer real data analyses.

Hydrologic Evaluation of the Global Precipitation Measurement Mission over the U.S.: Error Budget Analysis

This study investigates the hydrologic utility of satellite precipitation estimates from the Global Precipitation Measurement mission by comparing flood signals produced across the Continental United States by a ten-year span of in-situ, ground-based radar and satellite-based precipitation data. The flood characteristics generated with radar and satellite precipitation through a distributed hydrologic model are contrasted against reference stream gauge data as a method of integrated validation to assess and quantify error budgets between precipitation products by highlighting precipitation products’ accuracy, hydrologic scaling effects, and the impact of the hydrologic model. It is found that systematic and random errors associated with flood characteristics behave similarly to trends previously seen in precipitation rate errors between precipitation products, establishing a clear link through propagation of errors into the water cycle. Additionally, behaviors associated with both water balance and routing schemes within the hydrologic model were shown to affect outputs. Errors generated by water balance tend to cause overestimation of peak discharge values, while errors associated with routing tend to cause underestimation of flood durations and push flood timings earlier than the stream gauge reference.

Combining process-based model and machine learning to predict hydrological regimes in floodplain wetlands under climate change

Climate change has remarkable effects on the hydrological regime in floodplain wetlands. However, the hydrodynamic simulation under climate change conditions suffers from the uncertainty of the downstream water level boundary. In this study, an effective approach was developed by integrating an advanced machine learning algorithm and a process-based watershed hydrological model to predict the lake level under climate change. The developed approach was validated in a vital conservation wetland in the Ramsar Convention, the Poyang Lake floodplain wetland in China and utilized to simulate the hydrological regime in climate change. We found that the Long Short–term Memory (LSTM) performed relatively well in the simulation of water level, with coefficients of determination (R2) of 0.94 and 0.83 in the training and testing periods, respectively. The mean cumulative flooding time in the future period was slightly less than that in the baseline period, with a decreased range of 1.01 ∼ 12.05 days/year. The highest and mean water levels rose significantly in the wet season, with a risen range of 1.01 ∼ 3.3 and 1.56 ∼ 2.44 m, respectively, and the appearance of extreme flood events became more frequent. The maximum, minimum, and mean inflows for Poyang Lake in the dry season exhibited a remarkable reduction trend, especially for the minimum inflow, with a reduced range of 59.37%∼79.22%, indicating that more serious extreme drought events would appear in Poyang Lake. The developed approach has good performance for water level simulation and extreme runoff prediction, thus providing a viable way for future water resources management in floodplain wetlands.

Seasonal Abundance of Aedes Sollicitans and Aedes Taeniorhynchus Related to Temperature, Rainfall and Tidal Levels in Northeastern Florida.

The Anastasia Mosquito Control District, which manages mosquitoes in St. Johns County in northeastern Florida, has observed that the maximum numbers of the salt marsh mosquitoes, Aedes taeniorhynchus and Ae. sollicitan appeared to shift or change relative to each other, as evidenced by the Centers for Disease Control and Prevention (CDC) light trap data in the past 17 years. The aim of this study was to analyze environmental data to identify and explore these changes. Data from CDC light traps, temperature, rainfall, and tidal levels were analyzed using ANOVA. Analyses showed the 2 species had maximum abundance at different temperatures, which translated into seasonal differences with peaks of Ae. taeniorhynchus in the summer and, to a lesser extent, later in the year, and Ae. sollicitans with a peak in the autumn. This seasonal pattern was reflected in rainfall (more rain in autumn than in summer) and also, in the general area, in tidal levels (mean highest tide levels at the recording station were in autumn). The research demonstrated that simplifying the mosquito data, initially using only very high trap numbers (Mean ± 2 SD) that are important for control, identified, and made the seasonal pattern very obvious. The pattern was also observed using all the data but, although significant, was not as clear. Having identified tide as a potential driving variable, further research needs to detail spatial tidal patterns to identify areas and timing of flooding and explore the relationship between salinity and mosquito species and abundance. This is important as sea levels rise and climate changes, both potentially changing the mosquito situation and affecting control actions.

Energy-balance modeling of heterogeneous glacio-hydrological regimes at upper Indus

Study regionThe Upper Indus River Basin (UIB). Study focusThe UIB has experienced marked runoff change due to the accelerated glacier melting under climate warming. Nonetheless, the glacio-hydrological regime in the UIB remains unclear due to considerable uncertainties in precipitation data and glacio-hydrology modeling. Here, we used a state-of-the-art water and energy budget-based distributed glacio-hydrology model (WEB-DHM-S) that employed an energy-balance glacier module for both clean and debris-covered glaciers to analyze the hydrological regimes within the UIB during 2001–2020, particularly the spatial heterogeneity among the Himalaya-Karakoram-Hindu-Kush mountains. New hydrological insights for the regionResults indicated that the high-resolution ERA5-Land precipitation data showed the most reliable estimate (∼750 mm/yr) among available products, which was the model’s forcing data. Our results showed that the mean contributions of snow, glaciers, rainfall, and baseflow to total runoff in the UIB were 41.5%, 23.3%, 34.7%, and 0.5%, respectively. Glacial melting made the largest contribution to total runoff in the Karakoram (35.3%), while the smallest contribution was made in the Hindu Kush (15.9%). Further, we showed that glacial melting was highly sensitive to changes in air temperature and solar radiation inputs. In particular, fluctuating solar radiation could change the magnitude and timing of annual flood peaks in ice melting, which emphasized the crucial role of energy-related forcing data (besides the traditional precipitation and air temperature inputs) in glacio-hydrology modeling.

Performance of high temperature steam injection in horizontal wells of heavy oil reservoirs

Steam huff and puff and steam flooding are important development methods for heavy oil reservoirs. At present, there are certain deficiencies in the research on the timing and methods of steam stimulation, steam flooding, and subsequent steam flooding. In addition, the research on the mass and heat transfer characteristics of high temperature steam injection in heavy oil reservoirs is still in the initiation stage. This article first studies the high temperature steam flow model in the horizontal wellbore of the SAGD process. On this basis, a horizontal well pattern model was established through numerical simulation software to analyze the heat and mass transfer characteristics of high temperature steam huff and puff and high temperature steam flooding. Results show that: (a) for heavy oil reservoirs with high temperature steam injection huff and puff, the first cycle of steam injection ends (day 22): the temperature near the well pattern of the horizontal well pattern is higher. In the area between the horizontal well patterns, the temperature rise is not obvious; (b) when the high temperature steam injection huff and puff phase of the heavy oil reservoir ends (900 days), most of the heat energy is recovered, and the formation residual heat is less; (c) After the huff and puff transfer, the thermal connectivity between the horizontal well patterns is better.

FLUIDOGENIC LANDFORMS WITHIN THE PERMAFROST ZONE ON THE SHELF OF THE PECHORA AND KARA SEAS

The study is based on the results of multibeam echo-sounding and high-frequency seismic profiling during the 2018-2022 cruises of the R/V “Akademik Nikolai Strakhov” and “Akademik Boris Petrov”. Regular changes of morphometric parameters and the internal structure of pingo-like formations of the shelves of the Pechora and Kara seas were revealed. A morphometric analysis of pingo-like formations was carried out, which made it possible to draw conclusions about their relative age, as well as the role of near-bottom currents and slope processes in their modern dynamics. It was found that the density and morphological variety of pingo-like formations depend on the geological and tectonic features of the bottom area, the presence and nature of permafrost, the intensity of degassing, and the time of shelf flooding during the Holocene transgression. Pingo-like formations on the shelf, where the depth exceeds 70-80 m, emerged at the early stages of the Holocene transgression, and by now the permafrost there has largely thawed out. At the same time, pingo-like formations are still prominent in the relief and actively transformed by bottom currents, slope and, possibly, pseudovolcanic processes associated with ongoing degassing. Pingo-like formations are rare within shallow (up to 20-30 m) shelf areas close to the shore, and, apparently, continue their evolution at present. At the same time, the large thickness and continuity of permafrost prevent active fluid flow, acting as a seal. Pingo-like formations in the shallow-water zones are mainly cone-shaped mounds without intensive degassing. The density of pingo-like formations is maximum at the intermediate depths (from 20-30 to 70-80 m), in the presence of insular or discontinuous permafrost, under high fluid flow intensity within the fault zones and oil- and gas-bearing structures. Near-surface sediments in such areas are characterized by a combination of localized processes of heaving and active degassing. It predetermines a wide variety of the morphological types of pingo-like formations.Keywords: Arctic, bottom topography, degassing, pingo-like features, acoustic anomalies, multibeam echo sounding, seismoacoustic profiling

Trend analysis and identification of possible periods of change in the occurrence of extreme streamflow events in a tropical basin

Knowledge of the hydrological patterns of a river basin is important for environmental management in times of scarcity and floods. Among the variables that can influence river streamflow are precipitation and land use, which can intensify the occurrence of extreme events. The objective of this work is to identify trends in the time series of minimum and maximum streamflows, on a monthly and annual scale, in a tropical basin, based on non-parametric techniques. We also aim to analyze the main climatic and anthropic factors that can explain the changes in the rates of streamflow. The Mann-Kendall, modified Mann-Kendall and Pettitt tests were used at different levels of significance, as well as the Theil-Sen slope, to identify the magnitude of the trends found. The results showed that the minimum and maximum streamflows had a decreasing tendency in the dry period of the basin, specifically in October. Changes in the monthly time series occurred mainly in 2012. Precipitation behaved similarly to that observed in streamflows, with significant changes in the dry and rainy seasons, mainly in the north of the basin. Land use and land cover showed little variation in the analyzed period and was not considered a determining factor in streamflow changes. The application of different statistical methods allowed for finding satisfactory results for the behavior of water in the basin, while the analysis of climatic and anthropic factors made it possible to know their possible influences on changes in streamflow trends.

Identification of issues in disaster response to flooding, focusing on the time continuity between residents’ evacuation and rescue activities

Recently, there has been a growing concern regarding the severity of flood inundation, and the role of disaster response has become increasingly complex. As the number of problems to be addressed has been on the rise, the limits of individual disaster response capabilities have also been suggested. Therefore, disaster-response activities, whose contents change with time, should be regarded as a series of time-connected processes, and the issues of prolonged disaster responses should be reexamined. This study focused on the relationship between the evacuation of residents at the time of flooding and the subsequent rescue activities. Based on a flooding scenario in a real urban area, simulations were used to examine how different evacuation choices of residents may affect the subsequent rescue activities in the flooded area. The results show that the behavioral models desired in conventional studies of evacuation behavior do not necessarily lead to equally good outcomes throughout the entire disaster response. As a contribution of this study, a dilemma structure was found in which choosing risky evacuation behavior in the short term can ultimately improve the rescue situation. In addition, when residents themselves select their own evacuation behavior, it was found that the evacuation awareness of each resident affects the safety of other residents in the community and that the personal safety of a person is affected by the evacuation awareness of all community residents. It was suggested that not only the response of the government but also the attitude change of individual residents is important to solve this social dilemma.